COMMON DISEASE OF FISH , CAUSES, SYMPTOMS , TREATMENT & PREVENTIVE MEASURES
Fish diseases effect the survival and growth rates of fìsh under culture. Given that drug treatments are expensive, fìsh diseases invariably lead to lower harvest and higher cost. Fish farmers often suffer hefty economic losses due to fìsh diseases. To alleviate such losses, it is crucial to take precautions to prevent fìsh diseases and reduce pathogen levels in water bodies. It is also important to prevent water quality from deteriorating and to strengthen the natural resistance of the fìsh stock. Regular monitoring of fìsh health is an effective way to identify disease uses and appropriate treatments. One major cause of serious fìsh kill is overlooking the contagiousness of fìsh diseases and thus delaying treatment. As such, adequate care and treatment should be given to infected fish promptly.
Causes of fish diseases
There are three major causes of fish diseases:
Presence of environmental pathogens
. Low resistance of the fish stock
• Unsatisfactory water environment
Fish diseases, in various forms have been tormenting the aquaculturists ever since man learned the art of fish husbandry. The stability of a fish population in particular habit is very often disrupted by various factors viz., disease, habitat destruction, depletion of resources or other application of environmental stressors. Fish is in a State of equilibrium with the environment and a change in the environment parameters beyond the tolerance limit disturbs the equilibrium resulting in stress response in fish and making it valuable to fish disease. It should be understood that fish suffer from many diseases, of which from causative point of view they are classified as follows:-
(a) Non- parasitic infection by environmental stresses e.g.gas disease.
(b) Parasitic infection by Fungi, bacteria, protozoa, worms and crustacean.
Common fish diseases, their symptoms and control/ remedial measures:
Non – parasitic infection
A.Environmental diseases Gas disease (air embolism)
1.Depletion of oxygen————
Symptoms——-Mouth remains open, small bubbles beneath the skin, Gills look pale.
Control /remedial measures——-Aeration of water areas, growth of water hyacinth..
2. Growth of algae———
Symptoms——-Pond water turns green, fishes gape for like respiration.
Control /remedial measures——-Sprinkling of raw cow dung, growth of water hyacinth.
3. Increase of hydrogen sulphide————
Symptoms——-Pond bottom / muck smells like rotten eggs resulted in chocking respiratory.
Control /remedial measures——-Raking of pond bottom and change of water.
4. Excess of CO2 or high Ph of water———-
Symptoms——-Excessive secretion of mucus by gills and body surface.
Control /remedial measures——-Aeration of pond/ water areas.
B. Parasitic infection
1.Fungal disease——–
Symptoms——-Infects fry, fingerlings & adults becomes weak and lethargic, ulceration of skin, blindness, tuffs of minute white hair-like outgrowth in affected parts.
Control /remedial measures——– Dip treatment in 3% common salt for 5- 10 mins. – 1:2000 parts of copper sulphate (CuSo4) for 5- 10 mins. – 1:1000 parts of Potassium permanganate (KMno4) for 5-10 mins until fish shows distress
2. Gill rot————-
Symptoms——-Gill becomes greyish- white may finally drop off occurs during hottest time of the year.
Control /remedial measures——– Apply about 100 kgs/ ha quick lime in the pond – 3-5% common salt bath for 5 mins. – 5: 1000 parts KMno, bath for 5-10mins. – 8-12kgs/haCuSo4 applied in pond.
C.Bacterial disease
1. Fin and tail rot————
Symptoms——-White line appears in margin of fin and spreads to all parts of the body.
Control /remedial measures——– 1,2000 parts of CuSo4 for 1-2 mins – Painting/intense application the affected part by CuSo4 also helps
2. Ulcer————–
Symptoms——-Sores and ulcers appear in the body. Increases in size, gradually expose the muscles.
Control /remedial measures——– Badly infected fish be destroyed – 1:1000 parts of KMno4 applied in pond. – 1:2000 parts CuSo4 dip treatment for 1min for 3-4 days
3. Dropsy———–
Symptoms——-Accumulation of fluid inside the body cavity, scales protrudes
– 1:1000 parts KMno4 disinfect the pond – 5:1000 KMno4 dip treatment for 3 mins – 60 mg Chloromycetin in 4.5 ltr water bath the infected fish
4. Eye disease————
Symptoms——-Infects eye, optic nerves, brain of fish mostly Catla.
Control /remedial measures——– Initial stage Chloromycietin 8- 10 mg/ltr bath for 1 hour for 2- 3 days – Disinfect pond by 1:1000 parts KMno4
D.Protozoan diseases
1.Trichodiniasis———–
Symptoms——-Eye becomes opaque eyeball bursts. Pale colour of gills with a coating of cram layer of mucus.
Control /remedial measures——– Terramycin 100 mg / kg feed applied during 3 days. – 3-5% common salt bath hourly for 1 week. – 1:5000 parts formalin treatment in pond/ dip hourly for 7-10 days.
2. White gill spot disease———-
Symptoms——-Gills covered with white spots like pox.
Control /remedial measures——– 3-5% common salt bath for 5-10 mins. – Decreasing density of fish from affected pond . – 3-5% common salt solution bath for 5-10 mins.
3. Whit scale spot disease———
Symptoms——-Scales covered with white spots, falling of scales, perforation of scales.
Control /remedial measures——– Decreasing density of fishes in pond.
E.Helminth (worm disease)
1. Dactylogyrosis——————
Symptoms——-Excessive secretion of mucus in gills.
Control /remedial measures——– 3-5% common salt bath for 5-10 min. – 1:2000 part Acetic acid bath for 5 mins
2. Gyrodactylosis———–
Symptoms——-Mucus on caudal peduncle, infects skin and gills, dropping of scales.
Control /remedial measures——– 1:5000 parts fprmalin bath for 5- 10 mins. – Dip in 1.1 lakh parts of Picric acid for 1 hour.
3. Black spot disease———
Symptoms——-Black oval shaped patches and nodules on body.
Control /remedial measures——– Removal of moluscan population from water areas.
4. Ligulosis (tapeworms )———
Abdomen enlarges abnormally and body becomes dark.
Control /remedial measures——– Removal of birds from around affected areas.
F. Crustacean disease
1. Lemaeosis———-
Symptoms——-By anchor worms, buried deep in host tissue, rubbing against pond dykes or even bottom, becomes lethargic.
Control /remedial measures——– Gammaxene @ 1 ppm application in the pond
2. Ergasilosis———
Symptoms——-Irritation in gills and fins.
Control /remedial measures——– 5% common salt bath to the affected fishes.
3. Argulosis———
Symptoms——-Parasites visible on gills and body surface.
Control /remedial measures——-Removal of eggs of Argulas by hanging corrugated sheets in water and removing them and drying after a week to kill eggs.
Prevention of Fish Disease
a) Importance:
• It is difficult to identify the appearance of disease in its initial stage on account of the gregarious nature of fish in water which causes difficulties in observation, diagnosis and timely treatment.
• Apart from this, some effective drugs and measures to cure certain fish diseases are still not known well. Therefore, perfect preventive measures must be taken since this is a key link in fish disease control.
b) General Preventive Measures:
1. Increasing the internal resistance of fish is important in the prevention of diseases.
2. Selection of healthy fish seed.
3. Proper density and rational culture.
4. Careful management
5. Qualitatively uniform ration and fresh food.
6. Good water quality.
7. Prevention of fish body from injury.
Abolishing Pathogens and Controlling Its Spreading:
• Existence of pathogen is one among three factors (Host, Causative Agent and Environment) in outbreak of fish disease.
Controlling Measures
1. Thorough Pond Cleaning and Disinfection
• Bleaching powder (chlorinated lime) should be applied at the rate of 50 ppm in the pond.
• It readily kills all the wild fish species, molluscs, tadpoles, crabs and disinfects pond soil and water.
• In nursery and rearing ponds, it is desirable to use malathion at the rate of 0.25 ppm 4-5 days prior to stocking of fish seeds.
2. Disinfection of Appliances:
• Nets, gears, plastic wares and hapas should be sun-dried or immersed in a disinfected solution.
3. Disinfection of Fingerlings and Feeding Platform:
• Disinfection with mild concentration of potassium permanganate solution is helpful during the transfer of the fingerling to stocking tanks.
• The feeding platform can be disinfected by hanging bleaching powder cloth bags with mixture of copper sulphate and ferrous sulphate (ratio 5:2) near the feeding place.
• When fish come to the feeding place for feeding purpose, their skin will be automatically disinfected.
4. Proper Feeding:
• Fixed quality, quantity, time and place have to be followed for proper feeding.
• Any reduction in quality and quantity and variations in feed application and place may cause not only deficiency disease, but also will increase the susceptibility to many infectious diseases.
5. Segregation of year class fish population:
• Brood and older fish may serve as carriers of disease causing organisms without exhibiting any clinical symptoms.
• To avoid such risk, young fish should be segregated from the brood and older fish.
6. Spot removal of dead fish from the pond:
• Dead and sick fish should be removed as soon as it is located.
• The daily loss of fish should be recorded to provide valuable insight to the intensity of disease problem.
7. Chemoprophylaxis:
• Effective and inexpensive prophylactic measures against wide range of parasitic and microbial diseases are advisable as chemoprophylaxis.
• Occasional pond treatment with potassium permanganate at the rate of 2 -3 ppm and dip treatments with potassium permanganate at the rate of 500 – 1000 ppm for 1-2 minutes or short bath in 2-3% common salt solution is safe.
8. Immunoprophylaxis:
• Immunisation programme is gradually emerging as one of the most important measures for preventing infectious disease.
• Vaccine against Aeromonas hydrophila, Plexibacter columnaris, Edwardsiella tarda, E.ictaluri, Aerononas salmonicida, Yoreinia ruckeri, Vibrio angullaram and several viral pathogens such as IPNV (Infectious Pancreatic Necrosis Virus). CCVD (Channel Catfish Virus Disease), VHSV (Viral Haemorrhagic Septicaemia Virus), IHNV (Infectious Haemopoitic Necrosis Virus), etc. are being tried on large scale.
• Serodiagnostic methods that included Fluorescent Antibody Test (FAT), Enzyme Immuno Assay (EIA) and Passive Haemagglutination (PHA) are employed.
